Control means for refrigerating apparatus



March 14, 1939. c'. F. KETTERING CONTROL MEANS FOR REFRIGERATING APPARATUS Filed March 29; 1935 I E IYNVENTOR.

Patented Mar. 14, 1939 UNITED STATES CONTROL MEANS FOR REFRIGERATING APPARATUS Charles F. Kettering, Dayton, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a corporation Delaware Application March 29, 1935, Serial No. 13,732

4 Claims.

such as materials which swell or stretch according to changes in humidity, such as wood, paper, or hair. These materials, however, do not have fixed characteristics and require a delicate ad- 1 justment at the time of manufacture and also require adjustment during their life because of changes in characteristics.

It is an object of my invention to provide an improved humidity control device which is simple, easy to manufacture, and whose characteristics will not change throughout the normal life of the control device.

It is a further object of my invention to provide an improved combined control and indicating device responsive to the difference in temperature between the wet and dry bulb temperatures which is simple and reliable.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing, wherein a. preferred form of the present invention is clearly shown.

In the drawing:

The figure is a view of my improved humidity responsive control means together with a diagrammatic humidity control device.

Essentially, my improved control device comprises a pivot-ally mounted lJ-shaped tubing containing mercury and above the mercury on either leg of the U-tube is a volatile liquid. One of the legs of the U-tube is closed by a silver bulb, while the other is closed a wick which is kept moist from a supply of water. Thus, the volatile liquid in the silver bulb side is responsive to the dry bulb temperature, while the other side is responsive to .the wetbulb temperature. This causesthe vapor pressure in the two sides of the U-tube to correspond to the, dry bulb and the wet bulb cause the mercury to move in order to equalize the pressure. This changes the center of gravity of the tube and causes it to pivot and to control a set of contacts as well asan indicator.

Referring now more particularly to the drawing, there is shown a humidity control device generally designated by the reference character 20 comprising an evaporating means 22 located within a cabinet 24 provided with an electric motor driven fan 25 for circulating air from the chamber to be controlled tmough an opening 28 by a. bulb covered with temperature and to over the evaporating means and out an opening 30 in the top of the cabinet. Beneath the evaporating means is a pan 32 which collects any moisture which condenses and drips from the evaporating means 22. This pan is also provided with an electric heater 34 which may be energized to evaporate the water and to increase the humidity.

Either within or without the chamber, there is provided a refrigerant liquefying apparatusineluding a compressor 38 for compressing the reirigeran't and for forwarding the compressed refri'gerant to a condenser 38 where the compressed refrigerant is liquefied and collected in a receiver 40. From the receiver 40 the liquid refrigerant g is forwarded under the control of a thermostatic'valve 42 to the evaporating means 22 which absorbs heat and condenses moisture out of the air to reduce the humidity. The liquid refrigerant evaporates under reduced pressure in the evaporating means and is returned to the compressor through the return conduit 44. The thermostatic valve 42 is controlled by a thermostatic bulb 46 located in heat exchange relation with the return conduit 44.

The compressor is driven by an electric motor 48 supplied with electric energy through an electric circuit 50 which is controlled by a relay operated switch 52. The electric heater 361s supplied with electric energy through an electric circuit 54 under the control of a' relay operated switch 56. These electric circuits 50 and 54 are connected in parallel with the electric circuit 58 which supplies the electric energy to the motor driven fan 26.

In order to properly control the operation of the relay operated switches 52 and 56 to properly control the operation of the humidity control device, I have provided my improved form of humidity control device. This device generally designated by the reference character 60 .is located along with the humidity control cabinet 24 within the space or room which is to have its humidity controlled. This control device is pro-=- vided with a base 62 to which is pivoted a threearm member 64 having opposite clamping arms 66 and 68 which adiustably support by a. spring grip a U-shaped glass tube closed at its upper ends by the bulb 12 which is silvered and by the bulb 14 which is covered with a wick 16. The member 64 is pivotally mounted upon the pin 18 fixed to the base and has a pointer 88 extending downwardly which cooperates with a scale 82 mounted upon the base 62 to indicate the relative humidity.

The pointer also carries a set of contacts 84 which cooperate with the contacts 85 and 83 which are fixed to the base 62. The contact 86 is connected in series with the electric circuit 89 and the coil 90 oi! the relay operated switch-56 which controls the humidification while the contact 88 is connected in series with the electric circuit .92 and the coil 94 of the relay operated switch 52. These two circuits are energized by a battery 95 or other source of low voltage which is connected to the relay coils 90 and 94 and to the contacts 84 which are mounted upon an indicating arm or pointer 80.

The U-tube is partially filled with mercury and this maintains the center of gravity of the pivoted member below the pivot pin 18. The upper surface of the mercury is indicated by the reference character I02. Above the surface of the mercury dichloro methane (CHCIzF). closes the left leg of the U-tube 18 is preferably silver so that it will only be heat and not by radiant heat. However, if it is U-tube 10 is covered with a wick 16 which extends into a small container I04 which is carried by the pivot member 64 for keeping the wick 16 in a moist condition.

The moisture evaporates from the wick 16 and cools the bulb 14 liquid to create a vapor pressure corresponding to the dry bulb temperature. Inasmuch as the dry bulb temperature is practically always greater than the wet bulb temperature, and the vapor pressure is greater, the mercury will be forced by this diderence in vapor pressure to move a small amount toward the wet bulb 14. This movement or the mercury will tend to create an unbalance in the pivoted member. A small adjustable weight l08 threadedupon the threaded shaft I08 fixed to the pivoted member is provided for balancing any desired amount of the unbalance so created to cause the pivoted member to assume its vertical position at a desired relative humidity.

When this difierence is greater, the mercury will move sufficiently to cause the member 84 to move in a clockwise direction, thus moving the contact 84 into engagement withjthe contact 86, thereby closing the relay circuit 88 and then energizing the relay operated switch 56 to close the circuit 54 to the electric heater 34, thereby causing the water in the pan 32 to be vaporized and to raise the humidity of the room. The movement of the member 64 also moves the indicator 80 to indicate a lower humidity figure upon the scale 82. When the humidity is high, the pivoted member 64 moves in a counter-clockwise direction so that the indicator 80 indicates a higher humidity upon the scale 82 and when the humidity is sufliciently high, the contact 84 will engage contact 88 to close the relay circuit 92, thereby energizing the relay coil 94 it to close the switch 52 thereby energizing the viously when the and causing differential between the wet and dry bulb temper- U-tube 10, or by changing the amount of mercury in'the tube so as to raise or lower the center of gravity, thus bringing the center of gravity further from or nearer to the pivot point 18. Obcenter of gravity is close to the pivot point 18, the device will be extremely sensitive, whereas when the center of gravity is further from the pivot point, the device will be less sensitive. Thus, my control device has no moving parts except the simple pivoted member and the members fixed thereto. This makes the device simple and reliable, as well as easy to manufacture. There will be little trouble on account of wearing, since the only bearing is upon the pivot pin 18 and this may be made substantially frictionless by employing a knife edge or suitable lubrication.

While the form of embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In combination, a pair of receptacles, a conduit extending between said receptacles, variable pressure fluid in said receptacles, a dense fluid in said conduit, means for pivotally mounting said conduit and said receptacles, and means for wetting one of said receptacles including a supply of wetting fluid carried by said mounting means.

2. In combination, a support, a pair of bulbs, variable pressure fluid in said bulbs, an interconnecting conduit between said bulbs containing a liquid, means for pivotally mounting said bulbs and conduit on said support, and a wick for supplying water to one of said bulbs supported wholly by said means.

3. In combination, a support, a. pair of bulbs, variable pressure fluid in said bulbs, an interconnecting conduit between said bulbs containing a liquid, means for pivotally mounting said bulbs and conduit on said support, a wick for supplying water to one of said bulbs supported wholly by said means, a contact carried by said support, and a cooperating contact carried by said means.

4. In combination, a U-shaped conduit, receptacles on the ends of said conduit, means for pivotally supporting said conduit member with the U portion thereof in a substantially vertical plane, a liquid disposed in said conduit, variable pressure fluid'within said receptacles, means for wetting one of said receptacles, and means for vertically adjusting said U-shaped member with respect to said supporting means.

CHARLES F. KETTERING.

moving this weight, a certain 

